The company that owns a luxury jet that crashed and killed Mexican pop superstar Jenni Rivera is under investigation by the U.S. Drug Enforcement Administration, and the agency seized two of its planes earlier this year as part of the ongoing probe.

DEA spokeswoman Lisa Webb Johnson confirmed Thursday the planes owned by Las Vegas-based Starwood Management were seized in Texas and Arizona, but she declined to discuss details of the case. The agency also has subpoenaed all the company's records, including any correspondence it has had with a former Tijuana mayor who U.S. law enforcement officials have long suspected has ties to organized crime.

The man widely believed to be behind the aviation company is an ex-convict named Christian Esquino, 50, who has a long and checkered legal past. Corporate records list his sister-in-law as the company's only officer, but insurance companies that cover some of the firm's planes say in court documents that the woman is merely a front and that Esquino is the one in charge.

Esquino's legal woes date back decades. He pleaded guilty to a fraud charge that stemmed from a major drug investigation in Florida in the early 1990s and most recently was sentenced to two years in federal prison in a California aviation fraud case. Esquino, a Mexican citizen, was deported upon his release. Esquino and various other companies he has either been involved with or owns have also been sued for failing to pay millions of dollars in loans, according to court records.

The 43-year-old California-born Rivera died at the peak of her career when the plane she was traveling in nose-dived into the ground while flying from the northern Mexican city of Monterrey to the central city of Toluca early Sunday morning. She was perhaps the most successful female singer in grupero, a male-dominated Mexico regional style, and had branched out into acting and reality television.

It remained unclear Thursday exactly what caused the crash and why Rivera was on Esquino's plane. The 78-year-old pilot and five other people were also killed. Esquino was not on the plane.

The late singer's brother, Pedro Rivera Jr., said that he didn't know anything about the owner or why or how she ended up in his plane.

Esquino told the Los Angeles Times in a telephone interview from Mexico City that the singer was considering buying the aircraft from Starwood for $250,000 and the flight was offered as a test ride. He disputed reports that he owns Starwood, maintaining that he is merely the company's operations manager "with the expertise."

Esquino is no stranger to tangles with the law. He was indicted in the early 1990s along with 12 other defendants in a major federal drug investigation that claimed the suspects planned to sell more than 480 kilograms of cocaine, according to court records. He eventually pleaded guilty to conspiring to conceal money from the IRS and was sentenced to five years in prison, but much of the term was suspended for reasons that weren't immediately clear.

He served about five months in prison before being released.

Cynthia Hawkins, a former assistant U.S. attorney who handled the case and is now in private practice in Orlando, remembered the investigation well.

"It was huge," Hawkins said Thursday. "This was an international smuggling group."

She said the case began with the arrest of Robert Castoro, who was at the time considered one of the most prolific smugglers of marijuana and cocaine into Florida from direct ties to Colombian drug cartels in the 1980s. Castoro was convicted in 1988 and sentenced to life in prison, but he then began cooperating with authorities, leading to his sentence being reduced to just 10 years, Hawkins said.

"Castoro cooperated for years," she said. "We put hundreds of people in jail."

He eventually gave up another smuggler, Damian Tedone, who was indicted in the early 1990s along with Esquino and 11 others in a conspiracy involving drug smuggling in Florida in the 1980s at a time when the state was the epicenter of the nation's cocaine trade.

Tedone also cooperated with authorities and has since been released from prison. Telephone messages left Thursday for both Tedone and Castoro were not returned.

Esquino eventually pleaded guilty to the lesser offense of concealing money from the IRS.

Joseph Milchen, Esquino's attorney at the time, said Thursday the case eventually revolved around his client "bringing money into the United States without declaring it."

However, Milchen acknowledged that a plane purchased by Esquino was "used to smuggle drugs."

He denied his former client has ever had anything to do with illegal narcotics.

"The only thing he has ever done is with airplanes," Milchen said.

Court filings also indicate Esquino was sentenced to two years in federal prison after pleading guilty in 2004 to committing fraud involving aircraft he purchased in Mexico, then falsified the planes' log books and re-sold them in the United States.

Also in 2004, a federal judge ordered him and one of his companies to pay a creditor $6.2 million after being accused of failing to pay debts to a bank.

As the years passed, Esquino's troubles only grew.

In February this year, a Gulfstream G-1159A plane valued at $1.5 million was seized by the U.S. Marshals Service on behalf of the DEA after landing in Tucson on a flight that originated in Mexico.

Four months later, the DEA subpoenaed all of Starwood's records dating to Dec. 13, 2007, including federal and state income tax documents, bank deposit information, records on all company assets and sales, and the entity's relationship with Esquino and more than a dozen companies and individuals, including former Tijuana Mayor Jorge Hank-Rhon, a gambling mogul and a member of one of Mexico's most powerful families. U.S. law enforcement officials have long suspected Hank-Rhon is tied to organized crime but no allegations have been proven. He has consistently denied any criminal involvement.

He was arrested in Mexico last year on weapons charges and on suspicion of ordering the murder of his son's former girlfriend. He was later freed for lack of evidence.

In September, the DEA seized another Starwood plane — a 1977 Hawker 700 worth $1 million — after it landed in McAllen, Texas from a flight from Mexico.

Insurers of both aircraft have since filed complaints in federal court in Nevada seeking to have the Starwood policies nullified, in part, because they say Esquino lied in the application process when he noted he had never been indicted on drug-related criminal charges. Both companies said they would not have issued the policies had he been truthful.

Another attorney for Starwood has not responded to phone and email messages seeking comment, and no one was at the address listed at its Las Vegas headquarters. The address is a post office box in a shipping and mailing store located between a tuxedo rental shop and a supermarket in a shopping center several miles west of the Las Vegas Strip.